Technical advances in the identification, cloning, expression, and manipulation of nucleic acid molecules and the deciphering of the human genome have greatly accelerated the discovery of novel therapeutics. Rapid nucleic acid sequencing techniques can now generate sequence information at unprecedented rates and, coupled with computational analyses, allow the assembly of overlapping sequences into partial and entire genomes and the identification of polypeptide-encoding regions. A comparison of a predicted amino acid sequence against a database compilation of known amino acid sequences allows one to determine the extent of homology to previously identified sequences and/or structural landmarks. The cloning and expression of a polypeptide-encoding region of a nucleic acid molecule provides a polypeptide product for structural and functional analyses. The manipulation of nucleic acid molecules and encoded polypeptides may confer advantageous properties on a product for use as a therapeutic.
In spite of the significant technical advances in genome research over the past decade, the potential for the development of novel therapeutics based on the human genome is still largely unrealized. Many genes encoding potentially beneficial polypeptide therapeutics or those encoding polypeptides, which may act as “targets” for therapeutic molecules, have still not been identified. Accordingly, it is an object of the invention to identify novel polypeptides, and nucleic acid molecules encoding the same, which have diagnostic or therapeutic benefit.
Cytokines regulate a variety of cellular responses including proliferation, differentiation, and survival. Among the different classes of cytokines are the type I cytokines, which form four α-helical bundle structures that exhibit an up-up-down-down topology (Bazan, 1990, Immunol. Today 11:350-54; Leonard and O'Shea, 1998, Annu. Rev. Immunol. 16:293-322; Leonard, Fundamental Immunology 741-74 (Paul, ed., Lippincott Raven Publishers 4 ed., 1999)). Type I cytokines include many interleukins, such as IL-2, IL-3, IL-4, IL-5, IL-6, IL-7, IL-9, IL-11, IL-12, IL-13, and IL-15 as well as other hematologically-active molecules such as GM-CSF, erythropoietin, thrombopoietin, and molecules such as growth hormone and prolactin. Signaling by type I cytokines involves interaction with homodimers, heterodimers, or higher order receptor oligomers of the type I cytokine receptor superfamily. Ligand binding induces dimerization or higher order oligomerization, resulting in downstream signaling, in part involving the Jak-STAT pathway (Bazan, supra; Leonard and O'Shea, supra; Leonard, supra).
Thymic stromal lymphopoietin (TSLP) is a cytokine whose biological activities overlap with those of IL-7. For example, both TSLP and IL-7 induce tyrosine phosphorylation of the transcription factor Stat5 (Isaksen et al., 1999, J. Immunol. 163:5971-77). TSLP activity was originally identified in the conditioned medium of a thymic stromal cell line that supported the development of murine IgM+ B-cells from fetal liver hematopoietic progenitor cells (Friend et al., 1994 Exp. Hematol. 22:321-28). Moreover, TSLP can promote B-cell lymphopoiesis in long-term bone marrow cultures and can co-stimulate both thymocytes and mature T-cells (Friend et al., supra; Levin et al., 1999, J. Immunol. 162:677-83). TSLP may also serve as an extrinsic signal to specifically rearrange the T-cell receptor gamma locus (Candeias et al., 1997, Immunol. Lett. 57:9-14). Thus, the isolation and characterization of the cytokine receptor for TSLP would allow for the identification of compounds useful in treating TSLP-related diseases or conditions, such as those affecting B-cell development, T-cell development, T-cell receptor gene rearrangement, or regulation of the Stat5 transcription factor.